Building a Porsche 911 Carrera 2.7 RS
Sun, 05/16/2010 - 22:42 — admin
Back in 1973, the first 911 RS comprised of a lightened body, uprated Bilsteins and springs and a tuned engine. That formula still exists today, more or less but the 964 and 993 Carrera RS were a little different in that the body in white was actually taken out from the Zuffenhausen production line and carted to the Motorsport department at Weissach to be seam welded and stripped of the tar-like soundproofing. Needless to say this was a time consuming process especially for the specialized Motorsport technicians.
With more planning and forethought, Porsche had designed all future GT3s and GT3 RS models to be built entirely at the main production plant and not take up valuable time and space at their research, testing and motorsport facility at Weissach. However the progenitor of this species, the 2.7 RS was not so well thought out and did not have the same body strengthening as the subsequent 964 and 993 RS. It did get the superb 210 bhp Motorsport fettered Boxer flat-six engine and a remarkable (for that era) 5-speed manual gearbox as well as a rock hard RS spec suspension. (more on the 2.7 RS HERE)
The question then is how close does a conversion (replica is not strictly accurate) of a 1974 911 Carrera get to a 1973 Carrera 2.7 RS? Cosmetically many of the RS parts are available on the market complete with the fibreglass rear engine cover cum ducktail spoiler. The donor body in this project came from a 1974 vintage 911 Carrera and needed substantial restoration as even Porsche's corrosion resistance at that time was suspect.
Thanks to the mechanical similarity in the engine, body and chassis the conversion was a viable idea. To get the 2.7 RS' target weight of 975kg they had to remove as much weight from the body as possible and since this is a restoration cum conversion project starting from ground zero, this was entirely feasible. (the RS Touring has a bit more creature comforts and weighs in at 1075kg)
Below were the planned series of changes by Andy Tatlow of Flat Six Road & Race Engineering:
Complete overhaul with new pistons, valves, valve seats, valve guides, rockers and rocker shafts. The crankshaft was sent to Autofarm UK for shuffle pinning, line boring and oil pressure relief mods. New big end main bearings to withstand the high revs, new cylinder head studs to reduce any chance of fatigue failure, nose bearing, rod bolts and nuts, con rod bushes and a good used 964 oil pump. Service mechanical fuel injection pump to RS specification, overhaul throttle bodies and fit a new alternator. Finally repaint engine tin work and replate all parts to new standard.
Change all synchros, dog rings, 1st/2nd, 3rd/4th gear sliders, all needle roller bearings, seals and gaskets.
The original brakes which measured 282mm in front and 290mm at the rear while state-of-the-art back then in 1973 were woefully short on performance and stamina especially the fronts for a RS. New rear 3.2 Carrera brakes were put in place as well as new seals in rear calipers. However a pair of new Boxster 4-piston calipers and front brake discs were mooted but finally a pair of 964 vintage front 298mm discs were fitted instead. The beauty is these parts fit all the way back into a 1973 911 but there is no ABS so flat-spotting is a real possibility as is the occasional brake lock up.
Bilstein offers a specific RS damper set which is claimed to have been tuned for Nordschliefe. Together with that new front struts and lower A arms were fitted.
Fortunately back in the day the wiring of the electrical system was very simple unlike today which puts a huge question mark on the restorability of future modern day classics. But even back then electrics were expensive as those front side/indicator lamps and rear lamp/lenses cost a lot more than one would expect.
Windows and glass:
Part of the weight loss regime included using thinner gauge glass for the windscreen and windows as did the RS of that day. These real RS parts while available are hugely expensive and today Lexan or polycarbonate substitute is a less expensive alternative. New wind-up mechanisms and window lifters along its seals and trim were fitted.
Another key area where weight can be pared is the carpeting and insulation. A lightweight carpet set is available on the market as well as the replica RS lightweight bucket seats from World Wide Classics. Or one can opt to have no carpet at all. The door panels also has the RS theme with just a nylon pull-strap to open the doors. These items alone could have provided nearly half the total weight savings.
Strip body shell to bare metal, removal of sound deadening, repair corrosion as necessary, repaint in colour of choice as close to RS specs as possible, use of RS replica fibreglass panels. In this case racing white with green decals.
The cost of the project meant one could possibly buy a slightly used Cayman or end of 1st COE 911 GT3 but one only has to look at the asking prices of the real 2.7 RS to see this conversion is a real steal.
We would have loved to bring you a comparison with the real deal but there is none left for us to do a review as they have been exported long ago. Fortunately the owners of this particular 2.7 RS and 993 RS were quite happy have us feature the prized possessions.